Potentially harmful vapors and liquids are commonly found in areas of subsurface at chemical production facilities, manufacturing facilities, waste storage facilities, abandoned seepage basins, and at areas surrounding leaking sewer lines or other production lines or piping. Contaminants accumulate at and below the water table in the subsurface in such areas, but are also found, in gaseous and liquid form, at the "vadose zone" of the subsurface, the region of the subsurface above the water table. In industrial facilities, volatile organic compounds are common in the vadose zone of the subsurface.
Various devices and apparatuses are known for removing contaminants from the subsurface.
Existing apparatuses for removing subsurface gases and liquids, however, require application of outside forces and/or inputs. The apparatuses of U.S. Pat. Nos. 5,358,357, 5,172,764, 5,332,333, and 4,945,988 employ pumps for drawing fluid out of a subsurface and the apparatus of U.S. Pat. No. 3,980,138 employs a fan in order to draw fluid out of a subsurface.
Existing apparatuses for use in extracting underground contaminants are often complicated and costly to produce. They require an artificial energy source and must be activated for operation. Further, they require continuous maintenance and frequent replacement of component parts. Still further, contaminant removal rate is limited by diffusion and desorption of the contaminant through the subsurface pore structure. Active apparatuses apply more pumping force than is necessary to remove contaminants at a maximum rate and thus waste energy.
For mass removal of contaminants from a large area of contaminated subsurface, it is common practice to deploy a plurality of contaminant-removal apparatuses over the area. Obviously, problems of construction cost, energy consumption, operation costs, maintenance costs, and energy waste become increasingly significant when a system is deployed comprising several contaminant removal units.
In view of the above, there is a need for a low maintenance apparatus that removes underground contaminants inexpensively, and without application of outside mechanical force.